Lifting members in wear lining for rotary drums

ABSTRACT

This invention relates to lifting members for the wear lining of rotary drums employed in particle comminuting and sorting apparatus, such as mills, the members being placed in spaced relationship alongside of each other. Separate wear protecting elements are supported between each pair of lifting members, and the lifting members and the associated wear protecting elements are mounted along generatrices of the drum, i.e., the center line of each lifting member coincides with a drum generatrix.

Jan. 2, 1972 aredi 3333 8888 31111 I/ Ill] /4444 2222 4 u u u" 2 u u":Lv n t ahuflhm mw ec rS ba 8000K CPRFT 52799 25556 99999 lllll 69039Primary Examiner-Donald G. Kelly Attorney-Summers & Young Sltega AB,Ersmark, Czechoslovakia [22] Filed: 0ct.10,l969

[21] Appl.No.:

[57] ABSTRACT This invention relates to lifting members for the wearlining of [30] Foreign Application Priority Dam rotary drums employed inparticle comminuting and sorting apparatus, such as mills, the membersbeing placed in spaced relationship alongside of each other. Separatewear protecting Oct. 1l,l968Sweden................................l3730/68 elements are supportedbetween each pair of lifting members,

and the lifting members and the associated wear protecting elements aremounted along generatrices of the drum, i.e., the center line of eachlifting member coincides with a drum generatrix.

3 (Claims, 5 Drawing Figures References Cited 1,309.2l0Marcy............... ....24l/l83 X LIFTING MEMBERS IN WEAR lLllNINGF'Ollt ROTARY DRUMS BACKGROUND OF THE INVENTION In rotary drums, it isin many cases necessary, owing to wear stresses, to line the drum shellwith a wear-resistant lining. This is particularly the case in mills,such as ball mills or tube mills. The linings usually comprise plain orsectional plates secured by screwing onto the shell and end walls.Alternatively, shell and end wall plates may be bolted together withlifting members (so-called lifters) radially on end walls and along thegeneratrix on the shell. The lining may also be constructed orbar-shaped units placed side by side and held at the ends by clampingrings secured on the shell by screws. Said bar-shaped units may beplaced so as to deviate from the generatrix and thereby form a so-calledhelical lining. This brings about a sizing effect on the charge, in sucha way that grinding elements of greater dimension accumulate at theinlet end wall where the material to be ground is fed into the mill, andthe worn grinding elements are collected at the outlet end wall wherethe milling produce is finely ground. The sizing effect hereby resultsin an increase of grinding capacity.

A sizing effect is also obtained by the use of sectional platesaccording to U.S. Pat. No. 2,809,789. However, when the lifters on theseplates become worn, the sizing effect rapidly ceases and the plates intheir entirety must be exchanged. Such an exchange is uneconomic,because thereby a great portion of the lining is turned into scrap.

A corresponding sizing effect can be obtained by shell plates andseparate lifters, if the latter are screwed into rows of holes deviatingfrom the shell generatrices. The holes, thus, are to be drilled alonghelical lines deviating from said generatrices. In existing mills, withhole rows drilled in a conventional way along generatrices, it can beimpossible in many cases, for strength reasons, to drill new rows ofholes along helical lines. It further involves the drawback that everywear lining of steel, depending on different deviations from thegeneratrix and on varying mill diameters, must then be speciallymanufactured in forms rendering the correct helical shape for obtaininggood abutment to the shell. When using rubber, however, the plates andlifting members can be designed for being clamped along generatrices andyet be clamped to form a helix, because the members are elastomeric anddeform when being mounted.

SUMMARY OF THE INVENTION The present invention has as its object toovercome the disadvantage that hole rows are to be drilled in the shellalong helical lines, in order to avoid any reduction in the strength ofthe shell. By the present invention, existing hole rows are utilizedeven if one desires to vary the helix angle. Other advantages of theinvention will gradually become evident from the following description.

The lifting members according to the invention substantially arecharacterized in that the lifting portion of the lifting member, i.e.,that portion which meets the material being ground and which comprisesat least one side surface, so deviates from the generatrix that everysurface of the lifting portion, at that end of the side surface which islocated closest to the outlet end is nearer the centerline of thelifting member than at the inlet end of the drum.

According to the invention, the wear protection may comprise on singleplate, or several plates arranged one after the other, or severalbar-shaped units placed side by side, or suitable combinations thereof,and it may be made of any suitable material, for example rubber orsteel. The mounting of the wear lining can be carried out in anysuitable way, for example such as described in U.S. Pat. No. 3,107,867.The lifting members preferably are manufactured separately.

According to the invention, it is suitable that those surfaces of thelifting members which face to the center of the drum preferably tapertowards the outlet end of the drum with an angle deviating from thegeneratrix by up to It was found that when the lifting members are laidin along the generatrices on the shell and designed in a conventionalway, in many cases the segregation (sizing) will be inverse, in such away, that the heavy grinding elements collect at the outlet end and the(worn) grinding elements of a lighter weight have the tendency ofcollecting at the inlet end. For counteracting this inverse segregation,a deviation of one side surface of the lifting members by about O.5 isin many cases sufficient. For achieving a distinct sizing effect, withdrums having a diameter of up to 2.5 meters the deviation of one sidesurface of the lifting members preferably should be l.5-2.0 At greaterdrum diameters and with grinding elements of very great dimensions, theeffect will be improved by slight increase of the angle. If sizing isdesired to be effected on a very short distance, advantageously an angledeviation of l0-l5 is used. The aforesaid deviations were fbund to applyto numbers of revolutions usually applied (65-80 percent of the criticalnumber of revolutions).

BRIEF DESCRIPTION OF THE DRAWINGS Some embodiments of the invention aredescribed in the following, with reference to the accompanying drawingin which:

FIG. I shows a view seen from above of a lifting member according to theinvention,

FIG. 2 shows the same lifting member in a section along the line Il-IIin FIG. ll,

FIG. 3 shows a view seen from above of a second embodiment of theinvention, the invention,

FIG. 4 shows a view seen from above of a third embodiment of theinvention, and

FIG. 5 shows an application of the invention in a grate discharge mill.

FIGS. I and 2 show a lifting member 1 which, seen from above, has arectangular longitudinal shape. The lifting member is mounted along theshell generatn'x by means of suitable fastening means (not shown)possibly through each of the three holes 2 located along the liftingmember centerline 6 coinciding with a generatrix. The lifting memberholds the wear protecting elements 3 in such a manner, that the liftingmember is embedded in recesses in edge portions of the wear protectingelements. Of the two longitudinal side surfaces 4 and 5 of the liftingmember projecting upwardly above the wear protection, the side surface 4is the lifting side surface, and this side surface deviates from thegeneratrix of shell 7. The portion located above the wear protection,thus, tapers towards the outlet end of the drum. The angle deviation inthis case is about 2. As an alternative, the lifter can be given arounded top surface.

FIG. 3 shows a view of a second embodiment of a lifting member accordingto the invention. It differs from the embodiment in FIGS. I. and 2 onlyin that both side surfaces 8 and 9 of the lifting member which arelocated above the wear protection deviate from the shell generatrix. Thecenterline 6 of the lifting member coincides with a generatrix.

FIG. 4 shows a third embodiment of the invention according to which thelifting side 10 of the lifting member deviates from the generatrix byan, angular tooth shape which allows for a greater number of deviationdegrees from the generatrix.

FIG. 5 shows how the lifting members I according to the invention can bebuilt into a grate discharge mill II with inlet 12 and outlet 13. Thedrum is provided with lifting members I and wear protecting elements 3along the greater part of the inner shell surface. Immediately adjacentthe outlet 13 a grate I5 is mounted, the perforations of which determinethe maximum grain size of the ground product. The mill is charged withthe material to be ground and with grinding elements.

In many cases such the grinding elements, or at least part of them, areworn to such a size that they clog the grate, which causes troubles inthe form of capacity decline or operation interruptions or, at worst,operation breakdown. If, thus, the mill is equipped only with liftingmembers of the type designated by 1, such inconveniences can occur. Byinserting immediately before the grate one or several sections oflifting members of the type which in FIG. 5 is designated by 16, theaforesaid inconvenience can be eliminated.

Every section may comprise either only lifting members according tothe'invention, or a combination of lifting members according to theinvention and of conventional lifting members. The lifting side of thelifting member 16 with the lifting side surface 17 faces to the oppositedirection, so that the (worn) grinding elements of smaller dimensionswhich have caused the clogging of the grate are lifted back, and onlythe grinding elements of somewhat greater dimensions which are too largefor clogging the grate are allowed to be active at the grate. Thecritical" grinding elements of smaller dimensions are thereby subjectedto an additional wear or preferably are worn completely so as to havethe same grain size as the pulp in general. These elements are thencombined with the pulp and pass together with the pulp through thegrate. The result is a considerably reduced clogging of the grate. Ifthe grinding elements are of a grain size exceeding that of the pulpgrains, this will increase the wear in pumps, pipes and classifiers.

This utilization of the invention has been described in connection witha grate discharge mill, but the same principle, of course, can beapplied to other mills equipped with grate, for example partition wallsin sludge mills for control of the maximum grain size of grindingelements and/or the ground product. That side surface of the liftingmember 16 which lifts back can be designed with a deviation from theshell generatrix corresponding to the demand in question. The effect ofsaid "lifting back increases with increasing deviation. Experiments madewith l0l5 have succeeded well.

What I claim is:

1. In a rotary drum ofa comminuting mill or the like the improvementwhich comprises a plurality of elongate lifting members secured ingenerally side-by-side relationship along the interior surface of thedrum, each said lifting member lying with its longitudinal axis along ageneratrix of the cylindrical interior surface of the drum,

each said lifting element having one side surface which acts as thelifting surface during drum rotation and which is, over at least aportion of its length, disposed to form an acute angle to saidlongitudinal axis and thus also to the respective generatrix along whichthe respective lifting element lies whereby said one side surface liestoward the drum outlet end closer to said longitudinal axis than at theinlet end ofthe drum.

2. The apparatus of claim 1 which further includes at least on wearprotecting element between each pair of lifting elements.

3. The apparatus of claim 1 in which the surface of each said liftingelement which faces the center of said drum is tapered toward the outletend of the drum at an angle to the associated generatrix of as much as15.

1. In a rotary drum of a comminuting mill or the like the improvementwhich comprises: a plurality of elongate lifting members secured ingenerally side-by-side relationship along the interior surface of thedrum, each said lifting member lying with its longitudinal axis along ageneratrix of the cylindrical interior surface of the drum, each saidlifting element having one side surface which acts as the liftingsurface during drum rotation and which is, over at least a portion ofits length, disposed to form an acute angle to said longitudinal axisand thus also to the respective generatrix along which the respectivelifting element lies whereby said one side surface lies toward the drumoutlet end closer to said longitudinal axis than at the inlet end of thedrum.
 2. The apparatUs of claim 1 which further includes at least onewear protecting element between each pair of lifting elements.
 3. Theapparatus of claim 1 in which the surface of each said lifting elementwhich faces the center of said drum is tapered toward the outlet end ofthe drum at an angle to the associated generatrix of as much as 15*.